Optical imaging system with multiple imaging channel optical sensing

ABSTRACT

A method of calculating a volume of a drop pendant using a microprocessor. Included in the method are generating a gravity vector based on a direction of gravity with respect to the drop pendant; establishing a reference frame of the drop pendant for an image processing based on a reference point of the drop pendant and the gravity vector; generating a first reference line associated with the reference frame for representing an actual orientation of the drop pendant; generating a second reference line associated with the reference frame for representing a longitudinal axis of a chamber in which the drop pendant is located; comparing the first and second reference lines with respect to the gravity vector; and calculating the volume of the drop pendant based on the comparison of the first and second reference lines and the gravity vector.

CROSS REFERENCE

This is a Continuation application of U.S. patent application Ser. No.15/259,379 filed Sep. 8, 2016, which is a Continuation application ofU.S. patent application Ser. No. 13/828,744 filed Mar. 14, 2013, nowU.S. Pat. No. 9,476,825, which is a Continuation-In-Part applicationunder 35 U.S.C. § 120 of U.S. patent application Ser. No. 12/907,403filed Oct. 19, 2010, now U.S. Pat. No. 8,622,979, issued Jan. 7, 2014,all of which are incorporated by reference in their entireties.

TECHNICAL FIELD

The present disclosure relates generally to an infusion pump withchromatic multiplexing, in particular, the pump uses single or multiplelight sources, a single lens, mirrors, and beam combiners to enable useof a single color image sensor to provide distinct images for multipledistinct portions of the pump.

BACKGROUND

Monochrome image sensors are generally less costly than color imagesensors. However, for simultaneously received multiple images,monochrome sensors cannot be used to separate the respective images, forexample to generate, display, or operate upon the respective images,using conventional signal processing. For example, when a pixel in themonochrome sensor receives light, the sensor cannot determine which ofthe respective images the light pertains to.

SUMMARY

According to aspects illustrated herein, there is provided an opticalimaging system for use with an infusion tube having a drip chamberincluding a first portion with a drip tube, a second portion with anexit port, and a third portion located between the first and secondportions, the optical imaging system including: at least one lightsource for emitting at least two of first, second, or third spectrums oflight; an optics system including a single lens for receiving andtransmitting at least two of the first spectrum of light transmittedthrough the first portion, the second spectrum of light transmittedthrough the second portion, or the third spectrum of light transmittedthrough the third portion. The optical system includes a single imagesensor for receiving the at least two of the first, second, or thirdspectrums of light from the single lens and generating and transmittingdata characterizing the at least two of the first, second, or thirdspectrums of light received from the single lens. The imaging systemincludes a memory element for storing computer executable instructions;and at least one processor configured to execute the computer executableinstructions to generate, using the data, at least two of first, second,or third images of the first, second, or third portions, respectively.

According to aspects illustrated herein, there is provided an opticalimaging system for use with an infusion tube having a drip chamberincluding a first portion with a drip tube, a second portion with anexit port, and a third portion located between the first and secondportions, the optical imaging system including: a single light sourcefor emitting at least two of first, second, or third spectrums of light;and an optics system including a single lens for receiving andtransmitting at least two of: the first spectrum of light transmittedthrough the first portion; the second spectrum of light transmittedthrough the second portion; and the third spectrum of light transmittedthrough the third portion; and a single color image sensor for:receiving the at least two of the first, second, or third spectrums oflight from the single lens; and generating and transmitting datacharacterizing the at least two of the first, second, or third spectrumsof light received from the single lens. The imaging system includes amemory element for storing computer executable instructions, and atleast one processor configured to execute the computer executableinstructions to generate, using the data, at least two of first, second,or third images of the first, second, or third portions, respectively.

According to aspects illustrated herein, there is provided an opticalimaging system for use with an infusion tube having a drip chamberincluding a first portion with a drip tube, a second portion with anexit port, and a third portion located between the first and secondportions. The optical imaging system includes: at least one of a firstlight source for emitting a first spectrum of light only, a second lightsource for emitting a second spectrum of light only, or third source oflight for emitting a third spectrum of light only; and an optics systemincluding a single lens for receiving and transmitting at least one of:the first spectrum of light transmitted through the first portion; thesecond spectrum of light transmitted through the second portion; and thethird spectrum of light transmitted through the third portion. Theoptical system includes a single color image sensor for receiving the atleast one of the first, second, or third spectrums of light from thesingle lens and generating and transmitting data characterizing the atleast one of the first, second, or third spectrums of light receivedfrom the single lens. The imaging system includes a memory element forstoring computer executable instructions, and at least one processorconfigured to execute the computer executable instructions to generate,using the data, at least one of first, second, or third images of thefirst, second, or third portions, respectively. The first, second, andthird spectrums of light are free of overlapping wavelengths amongsteach other.

According to aspects illustrated herein, there is provided a method ofimaging an infusion tube having a drip chamber including a first portionwith a drip tube, a second portion with an exit port, and a thirdportion located between the first and second portions, including:storing, in a memory element, computer executable instructions; emittingat least two of first, second, or third spectrums of light from at leastone light source; receiving and transmitting, using a single lens atleast two of: the first spectrum of light transmitted through the firstportion; the second spectrum of light transmitted through the secondportion; or the third spectrum of light transmitted through the thirdportion; receiving, using a single image sensor, the at least two of thefirst, second, or third spectrums of light from the single lens;generating and transmitting, using the single image sensor datacharacterizing the at least two of the first, second, or third spectrumsof light received from the single lens; and executing, using the atleast one processor, the computer executable instructions to generate,using the data, at least two of first, second, or third images of thefirst, second, or third portions, respectively.

According to aspects illustrated herein, there is provided a method ofimaging an infusion tube having a drip chamber including a first portionwith a drip tube, a second portion with an exit port, and a thirdportion located between the first and second portions, including:storing computer executable instructions in a memory element; emitting,using a single light source, at least two of first, second, or thirdspectrums of light: receiving and transmitting, using a single lens atleast two of: the first spectrum of light transmitted through the firstportion; the second spectrum of light transmitted through the secondportion; or the third spectrum of light transmitted through the thirdportion; receiving, using a single color image sensor, the at least twoof the first, second, or third spectrums of light from the single lens;generating and transmitting, using a single color image sensor, datacharacterizing the at least two of the first, second, or third spectrumsof light received from the single lens; and executing, using at leastone processor, the computer executable instructions to generate, usingthe data, at least two of first, second, or third images of the first,second, or third portions, respectively.

According to aspects illustrated herein, there is provided a method ofimaging an infusion tube having a drip chamber including a first portionwith a drip tube, a second portion with an exit port, and a thirdportion located between the first and second portions, including:storing computer executable instructions in a memory element; andemitting at least one of a first spectrum of light only using a firstlight source, a second spectrum of light only using a second lightsource; or a third spectrum of light only using a third light source.The method includes: receiving and transmitting, using a single lens atleast one of: the first spectrum of light transmitted through the firstportion; the second spectrum of light transmitted through the secondportion; or the third spectrum of light transmitted through the thirdportion; receiving, using a single color image sensor, the at least oneof the first, second, or third spectrums of light from the single lens;generating and transmitting, using the single color image sensor, datacharacterizing the at least one of the first, second, or third spectrumsof light received from the single lens; and executing, using at leastone processor, the computer executable instructions to generate, usingthe data, at least one of first, second, or third images of the first,second, or third portions, respectively. The first, second, and thirdspectrums of light are free of overlapping wavelengths amongst eachother.

In one embodiment, a method of calculating a volume of a drop pendantusing a microprocessor is provided. Included in the method aregenerating a gravity vector based on a direction of gravity with respectto the drop pendant; establishing a reference frame of the drop pendantfor an image processing based on a reference point of the drop pendantand the gravity vector; generating a first reference line associatedwith the reference frame for representing an actual orientation of thedrop pendant; generating a second reference line associated with thereference frame for representing a longitudinal axis of a chamber inwhich the drop pendant is located; comparing the first and secondreference lines with respect to the gravity vector; and calculating thevolume of the drop pendant based on the comparison of the first andsecond reference lines and the gravity vector.

In another embodiment, an optical imaging system is provided forcalculating a volume of a drop pendant, and includes a microprocessorexecuting computer-executable instructions. Using the microprocessor, agravity vector is generated based on a direction of gravity with respectto the drop pendant. Also, a reference frame of the drop pendant isestablished for an image processing based on a reference point of thedrop pendant and the gravity vector. A first reference line associatedwith the reference frame is generated for representing an actualorientation of the drop pendant. A second reference line associated withthe reference frame is generated for representing a longitudinal axis ofa chamber in which the drop pendant is located. The first and secondreference lines are compared with respect to the gravity vector, and thevolume of the drop pendant is calculated based on the comparison of thefirst and second reference lines and the gravity vector.

BRIEF DESCRIPTION OF THE DRAWINGS

The nature and mode of operation of the present invention will now bemore fully described in the following detailed description of theinvention taken with the accompanying drawing figures, in which:

FIG. 1 is a schematic representation of definitions for an infusionpump;

FIG. 2 is a schematic block representation of an infusion pump with anoptical imaging system;

FIGS. 3A through 3F illustrate example embodiments of the illuminationsystem shown in FIG. 2 ;

FIGS. 4A through 4C are schematic representation of embodiments for anoptical system;

FIGS. 5A through 5C illustrate imaging processing definitions;

FIG. 6 illustrates an image of a drop including a circle at least partlyincluded within an outer boundary of the drop;

FIG. 7 is a flow chart illustrating operation of a pump with an opticalimaging system;

FIGS. 8A and 8B are schematic details for a pump implementing anoperation for determining a gravity vector;

FIGS. 9A and 9B are schematic details of a pump using light injection;

FIGS. 10A and 10B are schematic details of a pump with a meniscusdetection arrangement;

FIG. 11 is a schematic block representation of two infusion pumps withrespective optical imaging system in a primary and secondaryconfiguration;

FIG. 12 is a top-level block diagram illustrating operation of a pumpwith an optical imaging system;

FIG. 13 is a block diagram illustrating example signal processing andfeedback control for a pump with an optical imaging system;

FIG. 14 is a block diagram illustrating example digital filtering in apump with an optical imaging system;

FIG. 15 is a schematic representation of example spatial filtering in apump with an optical imaging system;

FIG. 16 is a schematic representation of an optical imaging system withmultiple imaging channel optical sensing and a single light source;

FIG. 17 is a schematic representation of an optical imaging system withmultiple imaging channel optical sensing and a single light source;

FIG. 18 is a schematic representation of an optical imaging system withmultiple imaging channel optical sensing and a single light source;

FIG. 19 is a schematic representation of an optical imaging system withmultiple imaging channel optical sensing and multiple light sources;and,

FIG. 20 is a schematic representation of an optical imaging system withtwo-channel optical imaging and a single light source.

DETAILED DESCRIPTION

At the outset, it should be appreciated that like drawing numbers ondifferent drawing views identify identical, or functionally similar,structural elements of the invention. While the present invention isdescribed with respect to what is presently considered to be thepreferred aspects, it is to be understood that the invention as claimedis not limited to the disclosed aspects.

Furthermore, it is understood that this invention is not limited to theparticular methodology, materials and modifications described and assuch may, of course, vary. It is also understood that the terminologyused herein is for the purpose of describing particular aspects only,and is not intended to limit the scope of the present invention, whichis limited only by the appended claims.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood to one of ordinary skill inthe art to which this invention belongs. Although any methods, devicesor materials similar or equivalent to those described herein can be usedin the practice or testing of the invention, the preferred methods,devices, and materials are now described.

FIG. 1 is a schematic representation of definitions for an infusionpump.

FIG. 2 is a schematic block representation of infusion pump 100 withoptical imaging system 102. Pump 100 includes specially programmedmicroprocessor 104, drip chamber 106 for connection to output tube 108,and drip tube 110 for connecting the drip chamber to a source of fluid112, for example, an IV bag. The drip tube includes end 114 disposedwithin the drip chamber. The imaging system includes illumination system118 and optical system 120. System 118 includes lighting element 122 fortransmitting light through wall 123 of the drip chamber to or arounddrop 124 of the fluid suspended from the end of the drip tube, forexample, one or both of the drip and end 114 are illuminated. System 118also controls illumination properties of the light transmitted to thedrop. System 120 receives, for example using optical sensor 126, lighttransmitted through the drop, or through or around end 114 andtransmits, to the microprocessor, data 129 regarding the received light.Pump 100 also includes pumping mechanism 127. In one embodiment, themechanism includes top and bottom flow restrictors and uses peristalticactuators, such as rollers, to displace fluid through tube 108.

FIGS. 3A through 3F illustrate example embodiments of system 118 in FIG.2 . As shown in FIG. 3A, light rays 128 from a collimated illuminationsystem are parallel. As shown in FIG. 3B, light rays 130 from a diffuseillumination system are emitted in a cone-shaped pattern from each lightemitting point on an illumination plane. As shown in FIG. 3C, light rays132 from illumination source 122 pass through telecentric lens 134 andare formed into ray bundles 136. The rays in bundles 136 are very nearlyparallel. The ray bundles provide sharp definition of image edges andminimize depth distortion. As shown in FIG. 3D, a structured lightingelement shapes illumination, for example, rays 138, so as to controlunwanted or stray light and to accentuate edges of an objecting beingilluminated. A structured lighting element can include barrier 139,disposed between an illumination source and an object being illuminated,for example, drop 124, to shape the illumination, for example, byblocking or altering light emanating from the source.

FIG. 3E illustrates the use of laser interference to project stripepatterns measure drop 124. Illumination source 122 includes laser lightsources 187. Sources 187 project light patterns consisting of manystripes at once, or of arbitrary fringes. This technique enables theacquisition of a multitude of samples regarding an image of drop 124,simultaneously. As seen from different viewpoints, the projected patternappears geometrically distorted due to the surface shape of the object.In one embodiment, patterns of parallel stripes are used; however, itshould be understood that other patterns can be used. The displacementof the stripes allows for an exact retrieval of the three dimensional(3D) coordinates of details on an object's surface, for example, thesurface of drop 124. Laser interference works with two wide planarfronts 189 from laser beams 191. The interference of the fronts resultsin regular, equidistant line, or interference, patterns 193. Differentpattern sizes can be obtained by changing the angle between the beams.The method allows for the exact and easy generation of very finepatterns with unlimited depth of field. FIG. 3E is a top view of pump100 and sources 187 are shown disposed radially about axis 195 for droptube 110. However, it should be understood that other configurations ofsources 187 with respect to the pump are possible, for example, parallelto axis 195.

FIG. 3F illustrates the use of projection lens 196 in system 118. InFIG. 3F, system 118 illumination source transmits light 197 through lens196. Surface 198 of the lens is modified as known in the art, forexample, etched or through deposition of chrome or other materials, toproduce a pattern on the surface. Light 197 passing through the lensprojects an image of the pattern on and about drop 124. In oneembodiment, projected pattern 199 is in the form of a constant-intervalbar and space square wave, such as a Ronchi Ruling, or Ronchi grating.

The illumination source for a structured lighting element can becollimated, diffuse, or telecentric. Structured illumination can controlunwanted or stray light and accentuate image edges. In one embodiment,the illumination system includes a telecentric lighting element. In oneembodiment, the illumination system includes a structured lightingelement.

Returning to FIG. 2 , microprocessor 104 includes data processingsegment 140 and data acquisition and control segment 142. The pump alsoincludes control panel 144, for example, any graphical user interfaceknown in the art. Output from the optical system, for example, data 129from sensor 126, is inputted to segment 142. Panel 144, or otheroperator input, is used to input a desired flow rate through the dripchamber, as well as other necessary data such as drug type and treatmentinformation. Microprocessor 104 can be any microprocessor known in theart.

Pump 100 uses optical sensing of pendant drops, that is drops hangingfrom or suspended from end 114, to measure fluid flow through the dripchamber to the output tube and to provide input to a closed-loop pumpcontrol process controlled by the microprocessor. Fluid from source 112flows through drip tube to end 114 of the drip tube. The fluid formsdrop 124 at end 114 and when conditions in the drip tube, discussedinfra, are suitable, the drop falls from end 114 into fluid 146 in thedrip chamber. In general, a pendant drop increases in volume inproportion to the outflow of fluid 146 from the drip chamber throughtube 108. That is, an increase in the volume of the pendant drop duringa time frame is equal to the volume of fluid passing from the dripchamber to tube 108 in the time period. The preceding relationship isbased on the following assumptions: the fluid from the source is notcompressible; source 112, the drip tube, the drip chamber, tube 108, anda patient to whom tube 108 is connected are closed to outsideatmosphere. Each measurement of the drop volume is processed to providea fluid volume (or mass) measurement. Successive measurements of dropvolume over known intervals of time are used by the microprocessor tocalculate the flow rate of fluid through the system.

Thus, in one embodiment, operation of pumping mechanism 127 iscontrolled by the microprocessor using the desired set point for flowthrough the drip chamber and data regarding a measured flow rate offluid through the drip chamber. For example, the microprocessor executesa feedback loop which compares the desired flow rate with the measuredflow rate, and adjusts the pumping mechanism to correct any deviationsbetween desired and measured flow rates.

FIGS. 4A through 4C are schematic representation of embodiments foroptical system 120. The embodiments shown in FIGS. 4A through 4C formreal, conjugate images, for example, of drop 124 on a focal plane arrayformed by sensor 126. FIGS. 4A and 4B use refractive optics, such assingle lens 148 or combinations 150 of lenses, respectively. FIG. 4Cshows refractive optics, such as combination 150 of lenses, andreflective optics, such as fold mirror 152. Lens 148, combination 150,and mirror 152 can be any lens, combination of lenses, or mirror knownin the art. Combination 150 may include different lenses in FIGS. 4B and4C.

Returning to FIG. 2 , in one embodiment, optical sensor 126 is a focalplane array formed by any means known in the art, including, but notlimited to a charge coupled device (CCD), a CMOS detector, or a hybridimaging array such as InGaAs bonded to a CMOS readout integratedcircuit. System 120 includes optics, such as lens 148, focused on thelocation of drop 124. It should be understood that other optics can beused in system 120.

In one embodiment, chamber 106 is substantially optically clear andsystem 118 directs light though the walls of the chamber to the opticalsystem, for example, sensor 126. The light can provide back or sideillumination of the drop. In one embodiment, system 102 is configuredsuch that drop 124 and the focal plane array are optical conjugates andthe focal plane array records an actual image of the drop. The imagingsystem captures drop images at a rate sufficient to observe the growthand detachment of a single drop.

In one embodiment, pump 100 satisfies two key metrics with respect toimaging drop 124. First, the frame rate (images per second) issufficient to capture a sequence of images as the drop grows in size anddetaches. Second, the exposure time (the amount of time the light iscollected on the sensor for each specific image) is short enough tofreeze the motion of the drop. Pump 100 generates images with clear edgedefinition, sufficient magnification (in terms of number of pixelsacross the drop), and a minimum number of artifacts such as glare.

In one embodiment, imaging system 102 and the microprocessor produce anaccurate image of the drop that is then analyzed as described infra todetermine the volume of the drop. Since the fluid drop has a uniformdensity, and any bubbles (occlusions) or entrainments are sufficientlysmall to be negligible, in one embodiment, only the outer surface of thedrop is measured to calculate the volume of the drop. The precedingmeasurement is accomplished by imaging the drop with sufficient spatialresolution to accurately measure the boundary surface. A numericintegral over this boundary then provides the droplet volume.

FIGS. 5A through 5C illustrate imaging processing definitions. In oneembodiment, a reference/alignment frame and an image scale (pixels permm) are established by locating end point 114 of the drip tube orifice,as shown in FIG. 5A. The end point has a known size and hence providesscale calibration. The end point also represents the top boundary of thedrop, which is used in volume calculations described infra. In oneembodiment, apex 154 of the drop (a point furthest from thefixed/reference point) is identified and used in the determination ofthe volume of the drop. For example, the optical system, for example,sensor 126, receives the light transmitted into or through the drip tubeand transmitting, to the microprocessor, data regarding the receivedlight. In one embodiment, the microprocessor is for determining, usingthe data, a boundary of end point 114 and using the boundary of endpoint 114 as a reference point for determining a volume, shape, orlocation of the drop, as further described infra.

In one embodiment, as further described infra, the direction of gravity(gravity vector 156) with respect to drop 124 is determined. A referencepoint, for example, the boundary of end point 114, and the gravityvector are used to establish a reference frame for the image processing.

In one embodiment, volume of drop 124 is calculated by using themicroprocessor to receive data 129 and generate an image of the dropfrom the data. The microprocessor locates an outer edge of the drop inthe image to define boundary 157 of the drop. The microprocessorintegrates an area enclosed by the boundary and calculates a volume ofrevolution for the drop with respect to axis 159 for the drop thatintersects the end of the drip tube, assuming symmetry of the drop withrespect to the axis.

The above calculation of the volume of drip 124 can be calculated usingat least two broad approaches. The first approach, termed BoundaryConstrained Volume and shown in FIG. 5B, uses the outer location of thedrop image to calculate the total volume. Each horizontal row 158 ofpixel data from the image has associated with it an outer left and rightboundary. The area between these boundaries is treated as the twodimensional projection of a circular disk volume (the symmetric volumeof rotation of the area). The drop image is integrated from end point114 to the apex by summing the volume of each row. Boundary ConstrainedVolume obtains maximum resolution for each row of data.

The second approach is termed Fit Constrained Volume and is shown inFIG. 5C. That is, the volume of drop 124 is determined by fitting aparametric function to the boundary image of the drop and integratingthe parametric function, again, assuming rotational symmetry. There area number of possible fitting algorithms, as discussed below, but theresult of any fit is a set of parameters to the assumed function thatrepresents entire boundary 157. Fit Constrained Volume smoothes out rowdetail.

In one embodiment, the microprocessor creates a plurality of temporallysuccessive images of the drop from data 129 and calculates a respectivevolume for the drop in each successive image or calculates respectivetime periods between detachment of successive drops from the end of thedrip tube. By temporally successive images, we mean a series of imagestaken over a time period in chronological order. The microprocessorcalculates a rate of increase for the volume of the drop using therespective volumes or the respective time periods. As noted above, flowout of the drip tube is substantially equal to the increase in thevolume of the drop; therefore, the time periods between drops detachingfrom the end of the drip tube can be correlated to the volume increasesof the successive drops. For example, in one embodiment, themicroprocessor calculates a respective volume for the drop in eachsuccessive image, for example, using operations described infra andsupra; calculates changes in the respective volumes; and calculates aflow rate of fluid to the output tube based on the changes in therespective volumes. In one embodiment, the microprocessor controlsmechanism 127 to match the calculated flow rate with a desired flowrate, for example, stored in the microprocessor.

In one embodiment, the microprocessor is for generating a free flowalarm or an out of bound condition alarm when the rate of increase forthe volume of the drops exceeds a predetermined value, for example,stored in the microprocessor. In one embodiment, the microprocessor isfor operating mechanism 127 to shut off flow to the output tube when thefree flow alarm or the out of bound condition alarm is generated. In oneembodiment the microprocessor generates a downstream occlusion alarmwhen the rate of increase of the volume of the drop is less than apredetermined value. In one embodiment, the microprocessor determinesthat a drop is absent from the end of the drip tube for a specifiedperiod of time and generates an empty bag alarm or an air-in-line alarm.

In one embodiment, the pump includes processor 163 used to operatemechanism 127 to shut off flow to the output tube when the free flowalarm or the out of bound condition alarm is generated. That is, as asafety and redundancy factor, a second microprocessor is used in thepump.

The drop is initially hanging from a fixed point in the drip chamber,for example, end 114. In one embodiment, the microprocessor is foridentifying when the drop detaches from the fixed point in the dripchamber as a means of determining when the drop has reached maximumvolume. The microprocessor makes the preceding identification bycreating a plurality of temporally successive images of the drop andanalyzing these images. By temporally successive images, we mean aseries of images taken over a time period in chronological order.

In one embodiment, the microprocessor identifies, in each successiveimage, a respective point in the boundary, for example, apex 154, anddetermines a distance of each respective point from end 114. Themicroprocessor then identifies two successive images of the drop inwhich the distance, noted above, in the second image in the successionis less than the distance in the first image in the succession. Thisdecrease of the distance indicates that the drop detached from the fixedpoint in the interval between the first and second images, which furtherindicates that the drop reached a maximum size in the first image. Themicroprocessor calculates the volume of the drop using the first image.

FIG. 6 illustrates image 160 of drop 124 including circle 162 at leastpartly included within outer boundary 164 of the drop. FIG. 6illustrates a specific example of the Fit Constrained Volume approach.In one embodiment, the microprocessor identifies respective circles 162within each temporally successive image. The circles are partiallydefined by a respective outer boundaries 164 of the temporallysuccessive images. The microprocessor identifies a respective location,with respect to the fixed point in the drip chamber, for each respectivecircle and calculates a volume of the drop from the data and using therespective circles. In one embodiment, identifying the respectivelocation for said each respective circle includes identifying the imagecorresponding to the largest size of the drop, for example, the lastimage before the drop detaches from the end point of the drip tube. Forexample, the microprocessor identifies a respective point on eachrespective circle at a furthest distance from the fixed point in thedrip chamber, for example, end point 114. The microprocessor thendetermines which of the respective points is furthest from the fixedpoint and identifies an image including the respective point furthestfrom the fixed point. That is, the microprocessor identifies the largestdrop by identifying the drop having the largest circle. In oneembodiment, the largest drop is identified by determining a first imagein which the distance of the apex from the fixed point decreases withrespect to the distance of the apex from the fixed point for a secondimage immediately preceding the first image. This decrease indicatesthat the drop detached from the fixed point in the interval between thefirst and second images, which further indicates that the drop reached amaximum size in the first image. The microprocessor calculates thevolume of the drop using the image including the respective pointfurthest from the fixed point.

In one embodiment, the microprocessor identifies the respective outerboundaries for each of the temporal images such that each outer boundaryincludes a respective edge of the drop furthest from the fixed point inthe drip chamber and the respective circle includes the respective edge.That is, the microprocessor aligns the circles described supra with theactual edges of the drops such that the points of the circles furthestfrom the fixed point, for example, end 114, are part of the edge of thedrop. In one embodiment, the microprocessor identifies respectivecircular arcs corresponding to the respective edges and including therespective circular arcs in the respective circles.

In one embodiment, identifying the image corresponding to the largestsize of the drop, for example, the last image before the drop detachesfrom the end point of the drip tube, includes using the center points ofthe circles. For example, the microprocessor calculates respectivecenter points 166 for the circles and calculates the positions of thecenter points with respect to the fixed point, for example, end point114. The microprocessor then determines which of the center points isfurthest from the fixed point and identifies an image including thecenter point furthest from the fixed point. That is, the microprocessoridentifies the largest drop by identifying the drop having the largestcircle. The microprocessor calculates the volume of the drop using theimage including the center point furthest from the fixed point.

FIG. 7 is a flow chart illustrating operation of pump 100 with anoptical imaging system. FIG. 7 illustrates an example algorithm usableby pump 100. It should be understood that other algorithms are usable bythe pump. The image of drop 124 is filtered and thresholded to create abinary image. Filter operations can include median filtering (to removeisolated glare), background and image uniformity correction (to removenoise sources due to dark noise, read noise, pixel non-uniformity, andillumination non-uniformity), and edge definition (using techniques suchas convolution or unsharp masking). The resulting images are thresholdedto yield binary images. A binary image consists of values that areeither black or white, with no intermediate grayscale values. The imagesare also processed (in parallel with the above operations) to find thereference location, for example, end point 114, using techniques such asfeature detection, pattern matching, or transform techniques such as theRadon transform. The end point location is used to form an image mask. Amask isolates a region of an image for further processing. Use of a maskincreases computational speed, as well as eliminates artifactinformation from being further processed.

In one embodiment, the binarized, masked images are then processedrow-by-row to find the extreme right- and left-boundaries. Thisboundary-constrained fit is one estimate of the drop edge shape. In oneembodiment, the images are also processed using a fit-constrainedalgorithm Such an algorithm applies constraints based on assumptionsabout the drop shape as discussed supra and infra. The constraints areused in a non-linear least squares optimization scheme to minimize theerror between the parameterized constraint function(s) and the set ofbinarized edge images.

The two different edge approximations are provided to an Edge Estimatoralgorithm that compares fit-constrained images to boundary-constrainedimages. In the simplest instantiation, the images are comparedrow-by-row. The boundary-constrained images are considered to be the“correct” result unless they deviate from the fit-constrained images bymore than a certain parameter (this parameter is adjusted duringcalibration). If the deviation is too large, the value from thefit-constrained image is used to replace that of theboundary-constrained image for that row. The above is intended toillustrate the concept behind the estimator. In actual use, moresophisticated algorithms are used to simultaneously optimize thedifference between the two initial estimates. An example of such analgorithm is a Kalman filter, but other algorithms familiar to thoseskilled in the art may also be utilized.

The output from the Edge Estimator also provides the location of theapex of the drop, which is for example, used to calculate thetime-dependent gravity vector. This operation requires access to priorestimates of the apex value (to calculate the change), and hence anumber of prior values are stored in a buffer. The gravity vector isrequired for some of the parametric fit functions that are used in thefit-constrained edge estimation algorithms. Hence, the gravity vector isused in a feedback loop for the edge fit algorithms.

FIGS. 8A and 8B are schematic details for pump 100 implementing anoperation for determining gravity vector 156. In one embodiment, system118 illuminates end point 114 and drop 124 and the optical system, forexample, sensor 126, receives light emanating from the end point andlight emanating from the drop and transmits data 129 regarding thereceived light. The microprocessor generates, using the data, respectiveimages of the drop and the end of the drip tube and locates an apex ofthe drop, the apex being a portion of the drop at a furthest distancefrom the end of the drip tube. The microprocessor determines, using thelocation of the apex, an orientation of the drop with respect to the endof the drip tube and calculates, using the orientation of the drop withrespect to the end of the drip tube, an orientation of the drip chamber.In one embodiment, the microprocessor compares the orientation of thedrip chamber to a set point, for example, a certain orientation withrespect to plumb stored in the microprocessor, and generates an out ofbound condition alarm when the orientation equals the set point orvaries from the set point by a specified amount. For example, if thedrip chamber is too far out of plumb, operation of pump 100 may becompromised and the alarm is generated.

For example, in FIG. 8A line 168 for the actual orientation of the dropand axis 170 for the drip chamber are co-linear, Since the drop mustnecessarily align with the forces of gravity (is plumb), the dripchamber is in a plumb orientation in FIG. 8A. Also, line 168 is alignedwith gravity vector 156. In FIG. 8B, lines 168 and 170 are not co-linearand the drip chamber is not plumb. Thus, in one embodiment, themicroprocessor generates lines 168 and 170 and compares the respectivelocations or orientation of the lines. That is, the microprocessorcalculates the orientation of the drip chamber with respect to thegravity vector. In one embodiment, when data 129 is used to generaterespective images over a period of time (temporally sequential images),the gravity vector is determined by measuring in the images of the endof the drip tube and the drop, the location of the apex of the pendantdrop as it grows over time and tracking the time-dependent directionalchange of the apexes over a series of these measurements. In oneembodiment, the boundary of end 114 is calculated as described supra andthe boundary is used as reference plane for calculating the orientationof the drop and/or the drip chamber.

In one embodiment, the illumination system controls illuminationproperties of the light illuminating the end of the drip tube and thedrop and the microprocessor: identifies respective boundaries of the endof the drip tube and the drop from the respective images; fits aparametric function to the respective boundaries; and integrating theparametric function to obtain a volume of the drop, for example, asdescribed above.

In one embodiment, the end point location, gravity vector, and optimaledge estimate are input to a volume calculation routine that integratesthe edge image using the “circular disk” assumption discussed above. Thelocation of the end of the drip tube is used to determine the upperlimit of integration, while the gravity vector is used to determine thedirection of the horizontal (at right angles to the gravity vector).These end and gravity data values are provided along with the volume asoutput from the algorithm. In one embodiment, the algorithm also passesout the parameters of the edge fit, as well as statistical data such asfit variances. In one embodiment, the preceding information is used inthe digital signal processing chain discussed below.

A number of methods can be used to fit a constraint to the measuredimage. In one embodiment, a “pendant drop” approach, involves solvingthe Laplace-Young equation (LYE) for surface tension. A drop hangingfrom a contact point (the end point) has a shape that is controlled bythe balance of surface tension (related to viscosity) and gravity. Theassumption is only strictly valid when the drop is in equilibrium;oscillations (due to vibration or pressure fluctuations) will distortthe drop shape from the Laplace-Young prediction. However, smalloscillations will not cause the fit to fail; in fact, the deviation froma fit is itself a good indicator of the presence of such oscillations.

In one embodiment, a Circular Hough Transform (CHT) is used on the imageto identify the component of the image that represents the curved bottomof the drop. While not strictly a “fit”, the CHT provides a parametricrepresentation of the drop that is characterized by the value and originof the radius of a circle. The CHT algorithm is representative of aconstraint that is determined or applied in a mathematical transformspace of the image. Other widely-used transforms, familiar to thoseskilled in the art, are the Fourier and wavelet transforms, as well asthe Radon transform.

The parametric fitting procedures described above apply strongconstraints on the possible location of the edge of the drop. Along withthe assumption of continuity (a fluid edge cannot deviate from itsneighbors over sufficiently short distances), and the requirement thatthe drop edge terminate at the drip tube orifice, the procedures areused to augment and correct the boundary-constrained image, as discussedabove. Other fitting procedures work similarly to those discussedherein.

FIGS. 9A and 9B are schematic details of pump 100 using light injection.Drip tube 110, drip chamber 106, tube 108, drop 124, imaging system 120,and sensor 126 are as described for FIG. 2 . Illumination system 118includes illumination source 172 for transmitting, or injecting, light174 into the drip tube. The light reflects off a plurality of portionsof internally facing surface 176 of the drip tube and the reflectedlight is transmitted through the end point 114 of the drip tube intointerior 177 of drop 124 such that the interior is uniformlyilluminated. The optical system receives light 178 transmitted from theinterior of the drop and transmits, to the computer processor, dataregarding the received light. The data regarding the received light canbe operated upon using any of the operations noted supra. For example,in one embodiment, the illumination system is for controllingillumination properties of the light transmitted to the drop, and theoptical system is for receiving light from the drop. The microprocessoris for: generating an image from the data, the image including aboundary of the drop; fitting a parametric function to the boundary ofthe drop; and integrating the parametric function to obtain a volume ofthe drop.

Thus, light 174 is formed into a beam, which is injected into thetransparent drip tube so as to undergo significant internal reflection(i.e., equal to or greater than the so-called “critical angle”). Thecylindrical bore of the tube causes the internal reflections to divergeinside the tube (filling the bore of the tube), while imperfections inthe tube surface introduce light scattering. The result is that the dropis illuminated internally. Under these conditions the imaging optics insystem 120 receive only light that is scattered from the drop surface(there is no direct ray path for the light to reach the lens). Inaddition to a high contrast edge image, this approach enables the use ofa very compact illumination element.

FIG. 10A is a schematic detail of pump 100 with a meniscus detectionarrangement. Drip tube 110, drip chamber 106, tube 108, and fluid 146are as described for FIG. 2 . Imaging system 102 includes light source,for example, a laser, for transmitting light 182 at an acute angle withrespect to longitudinal axis 184 for the drip chamber, into the dripchamber such that the light reflects, at the acute angle, off a surface186 of fluid pooled within the drip chamber. System 102 also includessensor, or position sensitive detector, 188 for receiving reflectedlight 182 and transmitting, to the computer processor, data regardingthe received light. The microprocessor is for calculating a position ofsurface 186 using the data regarding the received light.

The location on sensor 188 receiving light 182 depends on the locationof surface 186. Levels 190A and 190B show two possible levels for fluid146 and hence, two possible locations for surface 186. As seen in FIG.10B, light 182A and 182B reflecting from levels 190A and 190B,respectively, strike different portions of sensor 188. Themicroprocessor uses the difference between the locations on sensor 188to determine the level of fluid 146, that is, the meniscus, in the dripchamber. Sensor 188 can be any positional sensitive detector known inthe art, for example, a segmented sensor or a lateral sensor. In oneembodiment, the microprocessor generates an empty bag alarm or anair-in-line alarm for an instance in which the light transmitted fromlight source 188 is not received by the optical system, for example, thedrip chamber is empty or level 186 is so low that light 182 does notstrike fluid 146.

A segmented positional sensitive detector includes multiple activeareas, for example, four active areas, or quadrants, separated by asmall gap or dead region. When a symmetrical light spot is equallyincident on all the quadrant, the device generates four equal currentsand the spot is said to be located on the device's electrical center. Asthe spot translates across the active area, the current output for eachsegment can be used to calculate the position of the spot. A lateralpositional sensitive detector includes a single active element in whichthe photodiode surface resistance is used to determine position.Accurate position information is obtained independent of the light spotintensity profile, symmetry or size. The device response is uniformacross the detector aperture, with no dead space.

FIG. 10B is a schematic detail of pump 100 with a meniscus detectionarrangement. In one embodiment, imaging system 102 includes mirror 192on the opposite side of the drip tube to reflect light 182 back throughthe drip tube and beam splitter 194 to direct the reflected light tosensor 188. This configuration enables placement of all the electronicsfor the optical components on the same side of the tube.

The following provides further detail regarding meniscus levelmeasurement. The drip chamber remains partially filled with fluid at alltimes during operation. The air trapped in the drip chamber is inpressure equilibrium with the fluid above and below it. The differencein pressure across the air gap drives fluid out of the bottom of thedrip chamber and through downstream tubing 108. Fluid enters and leavesthe drip tube chamber continuously as the drop grows in volume, andhence the meniscus level of the fluid remains nearly constant. However,changes in the meniscus level can occur for several reasons: transientchanges may occur when a drop detaches and falls into the fluid below;or fluctuations may occur due to pressure oscillations in the fluid (dueto pump vibration, motion of the tubing set, or motion of the patient).These transient changes will fluctuate around a mean meniscus value, andhence do not indicate changes in flow rate over times long compared tothe characteristic fluctuation times.

Variations that change the mean meniscus level over longer times mayoccur due to changes in the external pressure environment (e.g., in atraveling vehicle or aircraft), changes in backpressure arising frommedical issues with the patient, or due to occlusions or othermalfunctions in the pumping process. These long-term meniscus levelchanges represent a concomitant change in the overall flow rate, and maybe used to provide a refinement to the flow measurements describedsupra. Hence, it may be desired to monitor the level of the meniscusduring the infusion, and to use the information derived therein as anindicator of operational problems with the infusion system, or as anadjunct to the primary optical flow measurement.

The method described above for measuring the level of fluid 146 uses thereflection of a light beam from the top surface of the fluid in the dripchamber. The axis of the reflected beam is shifted (deflected) laterallyas the fluid level changes, for example, as shown by light 182A and182B. The amount of deflection depends only on the fluid level change,and on the incident angle of the beam. Although a laser light source isshown in the figure, the technique is compatible with any light beam.Further, although the beam is shown freely propagating, the system mayalso incorporate lens elements to control the beam.

In one embodiment (not shown), sensor 126 (the imaging focal planearray) is used both for imaging drop 124 and measuring the meniscus offluid 146 via beam splitters and other simple optics. Sensor 126 can beshared in at least two ways: a portion of the sensor that is not usedfor pendant drop imaging can simultaneously record the deflected beam;or illumination system 118 for pendant drop imaging and meniscus levelmeasurement can be alternated in time, such that the sensor alternatelyrecords the drop image and the deflected beam image. For example, pump100 can combine the imaging systems 102 shown in FIGS. 2 and 10A/10B orshown in FIGS. 2 and 9A.

Thus, in one embodiment, system 102 includes a first light source, suchas light source 172 for transmitting light into the drip tube such thatthe light reflects off an internally facing surface of the drip tube,and the reflected light is transmitted through the end of the drip tubeinto an interior of a drop of the IV fluid hanging from the first end ofthe drip tube. System 102 also includes a second light source, such aslight source 188, transmitting light, at an acute angle with respect toa longitudinal axis for the drip chamber, into the drip chamber suchthat the light reflects, at the acute angle, off a surface for IV fluiddisposed within the drip chamber. Optical sensor 126 is for: receivingthe reflected light transmitted from the interior of the drop; receivingthe reflected light from the second light source; and transmitting, tothe computer processor, data regarding the received light from the firstand second light sources. The microprocessor is for calculating a volumeof the drop using the data regarding the light received from the firstlight source, and calculating a position of the surface of the using thedata regarding the light received from the second light source, asdescribed supra.

FIG. 11 is a schematic block representation of pump assemblies 200A and200B with respective optical imaging system in a primary and secondaryconfiguration. The assemblies include the components for pump 100described supra, with the exception of the processor and control panel.In general, the description above regarding the operation of pump 100 isapplicable to the operation of assemblies 200A and 200B. Assembly 200Ais connected to primary fluid source 112A. Pump 200B is connected toprimary fluid source 112B. Sources 112A and 112B are arranged in aprimary/secondary infusion configuration. For example, a primarymedication in source 112A is administrated in coordination with asecondary medication in source 112B. As is known in the art, in aprimary/secondary configuration, the medication in the secondary sourceis infused before the medication in the primary source. Tubings 108A and108B from pump mechanisms 127A and 127B, respectively, are connected tocommon tubing 202.

In one embodiment, a single processor and control panel, for example,processor 104 and panel 144 are used for assemblies 200A and 200B. Theprocessor operates assembly 200B according to appropriate protocolsuntil the regime for the fluid in source 112B is completed. Then, theprocessor automatically deactivates assembly 200B as required and beginsthe infusion of the fluid in source 112A. In one embodiment (not shown),each assembly has a separate processor and control panel or eachassembly has a separate processor and a common control panel.

FIG. 12 is a top-level block diagram illustrating operation of pump 100with an optical imaging system. In one embodiment, the volumemeasurement, and fit metrics if applicable, described above are fed intoa digital signal processing algorithm that calculates the flow rate andprovides feedback to the pump control system. Plant 210 includes source112, the drip chamber, the drip tube, and pump mechanism 127. Themicroprocessor outputs the Volume and Fit Metrics 212, which arefiltered by digital filter 214 in a portion of the microprocessor toprovide measured flow rate 216. The measured flow rate is compared withthe desired flow rate, for example, input into the microprocessor viapanel 144, closing the feedback loop for pump 100.

FIG. 13 is a block diagram illustrating example signal processing andfeedback control for pump 100 with an optical imaging system. Mechanism127 includes drive 218 and motor 220. Imaging data from system 102 isprocessed by image processing block 222 to generate a Measured DropVolume, and the results are input to filter block 224. The output of thefilter block is the Measured Flow Rate. The Measured Flow Rate iscompared to the Desired Flow Rate by comparator 226, providing the ErrorFlow Rate (error estimate). The Error Flow Rate feeds into a stagedseries of PID (Proportional, Integral, Derivative) control algorithms228. Each PID block operates on a successively faster time scale. Block228A controls the flow rate, block 228B controls the pump motor speed,and block 228C controls the pump motor current. The speed controlincorporates feedback from motor position encoder 230. The currentcontrol incorporates feedback from a motor current sensor in motor 220.

FIG. 14 is a block diagram illustrating example digital filtering inpump 100 with an optical imaging system. Filter 232 can be any filterknown in the art, for example, the general class of FIR/IIR filtersknown to those skilled in the art. A simple example is an FIR filterthat implements a time average over a number of samples.

FIG. 15 is a schematic representation of example spatial filtering inpump 100 with an optical imaging system. The goal of high resolution andedge definition for images of drop 124 are attained by illuminationtechniques, optical techniques, or both, for example, as describedsupra. In one embodiment, spatial filtering techniques are used in theoptics for system 120. For example, mask 240 at the back focal plane ofimaging system 102 modifies (via optical Fourier transform) the imagegenerated by the optical system, for example, sensor 126. A DC blockfilter is shown in FIG. 15 . This filter blocks the central cone of thetransmitted light and enhances edge images (associated with scatteredlight).

In one embodiment, the sensitivity of sensor 126 is matched to theillumination spectrum of the light source in system 118. In oneembodiment, sensor 126 is a low-cost visible light sensor (400-1000 nmwavelength) and source 122 generates light that is outside the range ofhuman visual perception (i.e., 800-1000 nm). In this case the operatorwill not be distracted by the bright illumination source.

It should be understood that pump 100 can be any pump mechanism or pumpapplication known in the art and is not limited to only IV infusion pumpapplications. In the case of a gravity-fed system, the pumping mechanismcan be replaced by a valve or flow restrictor, and still be compatiblewith the configurations and operations described supra.

FIG. 16 is a schematic representation of optical imaging system 300 withmultiple imaging channel optical sensing. In an example embodiment,system 300 is used with infusion tube 302 including drip chamber 304.Drip chamber 304 includes portion 306 with drip tube 308, portion 310including exit port 312, and portion 314 between portions 306 and 310.Output tube 316 can be connected to exit port 312 for flowing fluid outof drip chamber 304. Drip tube 308 is for connection to source of fluid317, for example, medication bag 317. System 300 includes at least onelight source 318 for emitting spectrums S1, S2, and S3 of light, andoptical system 319.

Light source 318 can be any light source known in the art, including,but not limited to a light-emitting diode (LED), an array of LEDs, alaser diode, an incandescent lamp, or a fluorescent lamp.

The optical system includes single lens 320 for receiving andtransmitting S1T, S2T, and S3T. S1T, S2T, and S3T include spectrums S1,S2, and S3, transmitted through portions 306, 310, and 314,respectively. Optics system 319 includes single image sensor 322 forreceiving S1T, S2T, and S3T from single lens 320. Sensor 322 generatesand transmits data 324, 326, and 328, characterizing S1T, S2T, and S3T,respectively, received by lens 320. System 300 includes memory element329 and at least one specially programmed processor 330. Memory element329 is configured to store computer executable instructions 331.Processor 330 is configured to execute instructions 331 to generate,using data 324, 326, and 328, images 332, 334, and 336 of portions 306,310, and 314, respectively.

By “characterize” we mean that the respective data describes, orquantifies, the spectrum of light, for example, providing parametersenabling generation of an image using the respective data. By “emittinglight” we mean that the element in questions generates the light. By“transmitted by” we mean passing light through the element in question,for example, light emitted by light source 318 passes through portions306, 310, and 314.

In an example embodiment, sensor 322 is a color image sensor. In anexample embodiment, light source 318 is a single light source.

In an example embodiment, portion 306 includes drop 338 pendant fromdrip tube 308 and image 332 includes an image of drop 338. Processor 330is configured to execute instructions 331 to determine a volume ofpendant drop 338 using image 332. The volume can be used in controlschemes to regulate flow of fluid through infusion tube 302.

In an example embodiment, portion 314 includes meniscus 342 for fluid indrip chamber 304 and image 336 includes an image of meniscus 342.Processor 330 is configured to execute instructions 331 to determine aposition of meniscus 342 using image 336. The position can be used incontrol and alarm schemes to regulate flow of fluid through infusiontube 302. In an example embodiment, air bubble 344 is present in portion310 and processor 330 is configured to execute instructions 331 todetermine a volume of air bubble 344 using image 334. The volume can beused in alarm schemes to ensure safe operation of infusion tube 302.

In an example embodiment, light source 318 emits red, blue, and greenspectrum light. In an example embodiment, S1T consists of one of thered, blue, or green spectrum light, S2T consists of one of the red,blue, or green spectrum light not included in S1T, and S3T consists ofone of the red, blue, or green spectrums of light not included in S1T orS2T. Thus each of S1T, S2T, and S3T consists of one of red, blue, orgreen light not included in the other of S1T, S2T, and S3T. That is,each of S1T, S2T, and S3T is different from the others. By “red spectrumlight” we mean light including wavelengths between about 610 nm and 675nm, with peak intensity at about 625 nm. By “blue spectrum light” wemean light including wavelengths between about 410 nm and 480 nm, withpeak intensity at about 470 nm. By “green spectrum light” we mean lightincluding wavelengths between about 500 nm and 575 nm, with peakintensity at about 525 nm. Thus, the respective spectrums for red, blue,and green light do not have overlapping wavelengths.

In an example embodiment, system 300 includes mirror 346 for reflectingone only of S1T, S2T, and S3T. For example, mirror 346A reflects S1T. Inan example embodiment, system 300 includes mirror 346A for reflectingone only of S1T, S2T, or S3T, and mirror 346B for reflecting anotheronly of S1T, S2T, or S3T, for example, S3T. In an example embodiment,system 300 includes beam combiner 348A for reflecting two only of S1T,S2T, or S3T. For example, in FIG. 16 , beam combiner 348A reflects S1Tand S3T and transmits S2T.

The following provides further detail regarding FIG. 16 . As describedbelow, various filtering operations are used to generate S1T, S2T, andS3T. Mirror 346A receives the combined red, blue, and green spectrumsemitted by source 318 and transmitted by portion 306 of drip chamber304, but reflects only spectrum S1T. Mirror 346B receives the combinedred, blue, and green spectrums emitted by source 318 and transmitted byportion 310 of output tube 316, but reflects only spectrum S3T. Thus,mirrors 346A and 346B are color-filtering.

In an example embodiment, sensor 322 is not monochrome, that is, sensor322 is a color image sensor. Beam combiner 348A transmits only spectrumS2T emitted by source 318 and transmitted by portion 314 of drip chamber304. Specifically, beam combiner 348A receives the combined red, blue,and green spectrums emitted by source 318 and transmitted by portion 314of drip chamber 304, but only transmits spectrum S2T. The beam combineralso reflects spectrum SiT reflected by mirror 346A and spectrum S3Treflected by mirror 346B. Note that the reflecting operations of beamcombiner 348A can be implemented using broad-band reflection, sincemirrors 346A and 346B have filtered out spectrums S2T and S3T andspectrums S1T and S2T, respectively.

FIG. 17 is a schematic representation of optical imaging system 400 withmultiple imaging channel optical sensing. The discussion regardingsystem 300 is applicable to pump 400 except as follows. In an exampleembodiment: optics system 319 includes a mirror for transmitting to oneof portions 306, 310, or 314 one only of S1, S2, or S3; or optics system319 includes a mirror for reflecting to one of portions 306, 310, or314, one only of S1, S2, or S3. For example: mirror 346C transmits S1 toportion 306 and reflects S2 and S3; mirror 346D transmits S3 andreflects S2 to portion 314; and mirror 346E reflects S3 to portion 310.In an example embodiment, mirror 346E is a broad-band reflecting mirror.

Mirror 346F is for reflecting spectrum S1T transmitted by portion 306 ofdrip chamber 304 to beam combiner 348A. In an example embodiment, mirror346F is a broad-band reflecting mirror. Mirror 346G is for reflectingspectrum S3T transmitted by portion 310 of drip chamber 304 to beamcombiner 348A. In an example embodiment, mirror 346G is a broad-bandreflecting mirror. Since the light entering beam combiner 348A has beenseparated into discrete spectrums, for example, light from mirror 346Gis only spectrum S2T, broad-band transmitting and reflecting operationscan be used in beam combiner 348A.

FIG. 18 is a schematic representation of optical imaging system 500 withmultiple imaging channel optical sensing. The respective discussionsregarding systems 300 and 400 are applicable to system 500 except asfollows. In an example embodiment, optical system 319 replaces a beamcombiner with mirrors 346H and 346I. Mirror 346H transmits S1T reflectedby mirror 346F and reflects S2T (from mirror 346D). Mirror 346Itransmits S3T (from mirror 346E) and reflects S1T (transmitted by mirror346H) and S2T (reflected by mirror 346H).

In FIG. 16 , length L1 of light source 318 must be sufficient to spanportions 306, 310, and 314, since light source 318 must emit lightdirectly through portions 306, 310, and 314. However, in FIGS. 17 and 18length L1 of light source 318 is considerably less, for example, equalonly to length L2 of portion 306. In FIGS. 17 and 18, light source 318is emitting light directly through portion 306; however, combinations ofmirrors are used to reflect light to portions 310 and 314. Thus, asmaller and less expensive device can be used for light source 318 inFIGS. 17 and 18 .

FIG. 19 is a schematic representation of optical imaging system 600 withmultiple imaging channel optical sensing. The discussion regardingsystem 300 is applicable to system 600 except as follows. System 600includes three light sources: light source 318A for emitting onlyspectrum S1, light source 318B for emitting only spectrum S2, and lightsource 318C for emitting only spectrum S3. Optical system 319 includesmirror 346J for reflecting S1T and mirror 346K for reflecting S3T. Beamcombiner 348B transmits S2T and reflects S1T and S3T. In an exampleembodiment, one or both of mirrors 346J and 346K are broad-bandreflecting mirrors. In an example embodiment, beam combiner 348B hasbroad-band transmitting and reflecting functionality.

In respective example embodiments for system 300, 400, 500, and 600,two-channel imaging is performed for only two of portions 306, 310, or314 and imaging is not performed on the remaining portion 306, 310, or314.

FIG. 20 is a schematic representation of optical imaging system 700 withtwo-channel optical imaging and a single light source. In system 700,chromatic multiplexing is implemented for only two of portions 306, 310,or 314. System 700 can use system 400 as a starting point. The followingdescribes differences between systems 400 and 700 as shown. In FIG. 20 ,two-channel optical imaging is implemented for portions 306 and 314.Mirrors 346E and 346G are removed. Mirror 346D no longer is required totransmit S3. Beam combiner 348A is no longer required to reflect S3T.Otherwise, the operations regarding portions 306 and 314 are the same asdescribed for FIG. 17 . In an example embodiment, imaging of portion 310is implemented by adding lens 702 to receive light S1T/S2T/S3Ttransmitted through portion 310 from light source 318. Lens 702transmits S1T/S2T/S3T to image sensor 704, which generates data 326.Processor 330 generates image 334 from data 326. Image sensor 704 can bemonochromatic, since chromatic multiplexing is not being implemented forportion 310.

Other combinations of two-channel optical sensing are possible forsystem 700 as is apparent to one skilled in the art. For example, mirror346D can be removed such that two-channel optical sensing is performedfor portions 306 and 310 only. Operations as described for portions 306and 310 for FIG. 17 are substantially the same. Lens 702 receivesS1T/S2T/S3T transmitted by portion 314 and transmits S1T/S2T/S3T toimage sensor 704, which generates data 328. Processor 330 generatesimage 336 from data 328. Image sensor 704 can be monochromatic. Forexample, mirror 346F can be removed such that two-channel opticalsensing is performed for portions 310 and 314 only. Operations asdescribed for portions 310 and 314 for FIG. 17 are substantially thesame. Lens 702 receives S1T/S2T/S3T transmitted by portion 306 andtransmits S1T/S2T/S3T to image sensor 704, which generates data 324.Processor 330 generates image 332 from data 324. Image sensor 704 can bemonochromatic. It should be understood that other configurations ofcomponents in system 400 are possible to implement two-channel opticalimaging. In an example embodiment, two-channel imaging is performed foronly two of portions 306, 310, or 314 and imaging is not performed onthe remaining portion 306, 310, or 314. That is, a second lens and imagesensor are not employed to image the remaining portion 306, 310, or 314.

System 300 can be modified for two-channel operation as is apparent toone skilled in the art. For example, two-channel operation can beimplemented for portions 306 and 314 only by removing mirror 346B.Operations as described for portions 306 and 314 for FIG. 16 aresubstantially the same. S1T/S2T/S3T from portion 310 is received by asecond lens (not shown) and transmitted to a second image sensor (notshown) that can be monochromatic. The second sensor generates data 326for generating image 334. For example, two-channel operation can beimplemented for portions 310 and 314 only by removing mirror 346A.Operations as described for portions 310 and 314 for FIG. 16 aresubstantially the same. S1T/S2T/S3T from portion 306 is received by asecond lens (not shown) and transmitted to a second image sensor (notshown) that can be monochromatic. The second sensor generates data 324for generating image 332. For example, two-channel operation can beimplemented for portions 306 and 310 only. Operations as described forportions 306 and 310 for FIG. 16 are substantially the same. S1T/S2T/S3Tfrom portion 314 is received by a second lens (not shown) andtransmitted to a second image sensor (not shown) that can bemonochromatic. The second sensor generates data 328 for generating image336. It should be understood that other configurations of components insystem 300 are possible to implement two-channel optical imaging. In anexample embodiment, two-channel imaging is performed for only two ofportions 306, 310, or 314 and imaging is not performed on the remainingportion 306, 310, or 314. That is, a second lens and image sensor arenot employed to image the remaining portion 306, 310, or 314.

System 500 can be modified for two-channel operation as is apparent toone skilled in the art. For example, to implement two-channel operationfor portions 306 and 314 only, mirror 346E can removed. Operations asdescribed for portions 306 and 314 for FIG. 18 are substantially thesame. S1T/S2T/S3T from portion 310 is received by a second lens (notshown) and transmitted a second image sensor (not shown) that can bemonochromatic. The second sensor generates data 326 for generating image334. For example, to implement two-channel operation for portions 310and 314 only, mirror 346F can removed. Operations as described forportions 310 and 314 for FIG. 18 are substantially the same. S1T/S2T/S3Tfrom portion 306 is received by a second lens (not shown) andtransmitted a second image sensor (not shown) that can be monochromatic.The second sensor generates data 324 for generating image 332. Forexample, to implement two-channel operation for portions 306 and 310only, mirrors 346D and 346H can removed. Operations as described forportions 306 and 310 for FIG. 18 are substantially the same. S1T/S2T/S3Tfrom portion 314 is received by a second lens (not shown) andtransmitted a second image sensor (not shown) that can be monochromatic.The second sensor generates data 328 for generating image 336. It shouldbe understood that other configurations of components in system 500 arepossible to implement two-channel optical imaging. In an exampleembodiment, two-channel imaging is performed for only two of portions306, 310, or 314 and imaging is not performed on the remaining portion306, 310, or 314. That is, a second lens and image sensor are notemployed to image the remaining portion 306, 310, or 314.

System 600 can be modified for two-channel operation as is apparent toone skilled in the art. For example, to implement two-channel operationfor portions 306 and 314 only, mirror 346K can removed. Operations asdescribed for portions 306 and 314 for FIG. 19 are substantially thesame. S3T from portion 310 is received by a second lens (not shown) andtransmitted a second image sensor (not shown) that can be monochromatic.Light source 318C can be broadband (emit S1/S2/S3). The second sensorgenerates data 326 for generating image 334. For example, to implementtwo-channel operation for portions 310 and 314 only, mirror 346J canremoved. Operations as described for portions 310 and 314 for FIG. 19are substantially the same. S1T from portion 306 is received by a secondlens (not shown) and transmitted a second image sensor (not shown) thatcan be monochromatic. Light source 318A can be broadband (emitS1/S2/S3). The second sensor generates data 324 for generating image332. For example, to implement two-channel operation for portions 306and 310 only, S2T from portion 314 is received by a second lens (notshown) and transmitted a second image sensor (not shown) that can bemonochromatic. Light source 318B can be broadband (emit S1/S2/S3). Thesecond sensor generates data 328 for generating image 336. Operations asdescribed for portions 306 and 310 for FIG. 19 are substantially thesame. It should be understood that other configurations of components insystem 600 are possible to implement two-channel optical imaging. In anexample embodiment, two-channel imaging is performed for only two ofportions 306, 310, or 314 and imaging is not performed on the remainingportion 306, 310, or 314. That is, a second lens and image sensor arenot employed to image the remaining portion 306, 310, or 314.

For the sake of brevity, portions of the following discussion aredirected to system 300 in FIG. 16 ; however, it should be understoodthat the discussion is applicable to FIGS. 17 through 19 as well.Further, the following discussion is directed to embodiments in whichmultiple channel optical sensing is implemented for all three ofportions 306, 310, and 314. However, it should be understood that thediscussion is applicable to the two-channel embodiments discussed above.Using a single lens, such as lens 320, and image sensor, such as sensor322, in place of three lens and sensors, reduces cost and complexity ofsystem 300. All three spectrums S1, S2, and S3, transmitted by lens 320are received simultaneously by single image sensor 322. However, ifsensor 322 is a monochrome sensor, conventional signal processing cannotbe used to generate images 332, 334, and 346. For example, a monochromesensor cannot distinguish among the red, blue, and green and cannot useconventional signal processing to separate spectrums S1T, S2T, and S3Tto generate images 332, 334, and 346. Advantageously, system 300 uses acolor imaging sensor for sensor 322, which is able to distinguish amongspectrums S1T, S2T, and S3T.

Since a single, separate, respective color from the red, blue, and greenspectrums is used for each of spectrums S1T, S2T, and S3T, imager 322 isable to transmit data 324, 326, and 328 for single respective spectrumsand hence, a single respective image of each of portions 306, 310, or314 can be generated using conventional signal processing operations.For example, spectrums S1T, S2T, and S3T can consist of red, blue, andgreen spectrum light, respectively. The red-responsive pixels of thesensor pick up spectrum S1T, the blue-responsive pixels of the sensorpick up spectrum S2T, and the green-responsive pixels of the sensor pickup spectrum S3T.

Thus, the red-responsive pixels record an image of drop 338, theblue-responsive pixels record an image of meniscus 342, and thegreen-responsive pixels record an image of portion 310. Thus, each groupof responsive pixels (for example, the red-responsive pixels) remainunresponsive to, in essence filtering out, images from the other imagescorresponding to the remaining groups of responsive pixels (for example,the blue and green-responsive pixels). Thus, there is no overlap ofspectrums or images included in data transmitted to processor 330 andconventional signal processing can be used to generate images 332, 334,and 346.

The use of broad-band reflecting mirrors/reflecting operations ratherthan color filtering reflecting and transmitting can reduce the cost ofrespective optics systems 319 in FIGS. 17 through 19 .

In an example embodiment (not shown), a single lens, such as lens 320,and a single monochrome image sensor are used in a time multiplexingarrangement in an infusion pump. For example, using FIG. 19 as areference, each of light sources 318A/B/C emits the same spectrum oflight. The emitted light is transmitted through portions of an infusiontube, such as infusion tube 302, analogous to portions 306, 310, and 314described supra. Via an arrangement similar to mirrors 346A/346B andbeam combiner 348A, the light, transmitted through the analogousportions, is transmitted to the single lens, which transmits the lightto a processor, such as processor 330. As noted above, a monochromesensor cannot distinguish, using conventional signal processing, threesimultaneously received images. However, in the example embodiment, thethree light sources are sequentially energized such that only one lightsource is energized per image frame of the image sensor. For example, ina first frame, the light source emitting light transmitted through theportion analogous to portion 306 is energized, in the next frame, thelight source emitting light transmitted through the portion analogous toportion 310 is energized, and in the next frame the light sourceemitting light transmitted through the portion analogous to portion 314is energized. The processor receives only one image per frame and isable to transmit respective data for each image in each frame to theprocessor. The processor in turn is able to generate separate images foreach of the analogous portions of the pump. The use of a monochromeimage sensor and three backlights emitting the same spectrum reduces thecost of the pump in the example embodiment.

The following discussion provides further detail regarding FIGS. 16through 19 . It should be understood that the following discussion isapplicable to the two-channel embodiments discussed above. In an exampleembodiment, lens elements (not shown) can be added to respective imagepaths (paths traversed by light from a light source to an image sensor)for systems 300 through 600 to compensate for unequal image paths. In anexample embodiment, a spectrum of light in the near infra-red range (forexample, between 700 nm and 1,000 nm) can be used to illuminate portions306, 310, or 314. In an example embodiment, light source 318 and/orlight sources 318A/B/C are LEDs and the LEDs are pulsed to improveoperating efficiency or create a strobe effect which eliminates motionblur of moving artifacts. The pulsing is synchronized with the shutterspeed of image sensor 322. In an example embodiment, the generalconfiguration of FIG. 18 , which does not use a beam combiner, ismodified by using three light sources as shown in FIG. 19 . Theresulting combination uses fewer mirrors than shown in FIG. 18 ,reducing the cost of the embodiment.

Thus, it is seen that the objects of the invention are efficientlyobtained, although changes and modifications to the invention should bereadily apparent to those having ordinary skill in the art, withoutdeparting from the spirit or scope of the invention as claimed. Althoughthe invention is described by reference to a specific preferredembodiment, it is clear that variations can be made without departingfrom the scope or spirit of the invention as claimed.

What is claimed is:
 1. For an infusion pump having a drip chamber havinga longitudinal axis, the drip chamber being coupled to an output tubeand a drip tube coupling the drip chamber to a source of fluid forproviding a pool of the fluid within the drip chamber, acomputer-implemented method of calculating a position of a meniscus ofthe pool of the fluid within the drip chamber, the method comprising:transmitting a beam of light from a light source at an incident anglethrough a wall of the drip chamber to a surface defined by the meniscus,the incident angle being an oblique angle with respect to thelongitudinal axis of the drip chamber, wherein the light is reflectedfrom the surface; receiving the reflected light at a position of apositional sensitive detector, wherein the position of the positionalsensitive detector that receives the reflected light depends at least onthe incident angle and the position of the meniscus; transmitting dataregarding the received light from the positional sensitive detector to amicroprocessor; and calculating, using the microprocessor, the positionof the meniscus based on the transmitted data.
 2. The method of claim 1,wherein the longitudinal axis is parallel to the wall of the dripchamber.
 3. The method of claim 2, wherein the incident angle is anacute angle with respect to the longitudinal axis of the drip chamber.